diff --git a/spectrum.py b/spectrum.py
index 0f2e68b..e313564 100644
--- a/spectrum.py
+++ b/spectrum.py
@@ -57,7 +57,7 @@ while i < len( argv ):
         if arg[1] == '-': # not elif because arg can change after last if
             if arg == '--help':
                 print( 'spectrum.py [options...] filename\
-                      \n    -w --wavelength wavelength calibration file, default to no calibration.\
+                      \n    -w --wavelength  wavelength calibration file, default to no calibration.\
                       \n                     No calibration means no wavelength interpolation\
                       \n    -i --intensity   intensity calibration file, default to no calibration.\
                       \n                     No calibration means no intensity interpolation\